Question

Predict the products of electrolysis in each of the following:

(i) An aqueous solution of AgNO₃ with silver electrodes.

(ii) An aqueous solution of AgNO₃with platinum electrodes.

(iii) A dilute solution of H₂SO₄with platinum electrodes.

(iv) An aqueous solution of CuCl₂ with platinum electrodes.

Answer 1

(i) At cathode:

The following reduction reactions compete to take place at the cathode.

The reaction with a higher value of takes place at the cathode. Therefore, deposition of silver will take place at the cathode.

At anode:

The Ag anode is attacked by ions. Therefore, the silver electrode at the anode dissolves in the solution to form Ag⁺.

(ii) At cathode:

The following reduction reactions compete to take place at the cathode.

The reaction with a higher value of takes place at the cathode. Therefore, deposition of silver will take place at the cathode.

At anode:

Since Pt electrodes are inert, the anode is not attacked by ions. Therefore, OH⁻ or ions can be oxidized at the anode. But OH⁻ ions having a lower discharge potential and get preference and decompose to liberate O₂.

(iii) At the cathode, the following reduction reaction occurs to produce H₂ gas.

At the anode, the following processes are possible.

For dilute sulphuric acid, reaction (i) is preferred to produce O₂ gas. But for concentrated sulphuric acid, reaction (ii) occurs.

(iv) At cathode:

The following reduction reactions compete to take place at the cathode.

The reaction with a higher value of takes place at the cathode. Therefore, deposition of copper will take place at the cathode.

At anode:
The following oxidation reactions are possible at the anode.

At the anode, the reaction with a lower value of is preferred. But due to the over-potential of oxygen, Cl⁻ gets oxidized at the anode to produce Cl₂ gas.